The present invention relates to a picture coding apparatus and the method, and is suitably applicable to, for example, a picture coding apparatus that divides and codes the predetermined picture data into the plural picture data composed of different resolutions.
Heretofore, as this sort of picture coding apparatus, there is such a device that hierarchically codes an input picture data using a hierarchical coding scheme such as the pyramidal coding scheme (Japanese Patent Publication No. 142836/1993). In this picture coding apparatus, the high resolution input picture data is treated as the first hierarchy data, and the second hierarchy data which has a lower resolution than the first hierarchy data, the third hierarchy data which has a lower resolution than the second hierarchy data, . . . are formed sequentially and recursively, and these plural hierarchy data are transmitted through a transmission line which is composed of one communication channel or a recording/reproducing path.
A picture decoding device which decodes the plural hierarchy data is able to decode all of the plural hierarchy data, and also is able to select and decode the desired one out of the hierarchy data, based on the resolution of a corresponding television monitor and the like. By decoding only the desired hierarchy data out of thus hierarchized plural hierarchy data, the desired picture data can be obtained, with the irreducible minimum of transmitting data quantity.
As shown in FIG. 1, the picture coding apparatus which realizes this hierarchical coding such as a four hierarchy coding has decimating filters 2, 3, 4 and interpolating filters 5, 6, 7 both for three stages, and progressively forms the compacted picture data D2, D3, D4 of which the resolutions are low by the decimating filters 2, 3, 4 of each stage with respect to the input picture data D1, and returns the resolutions of the compacted picture data D2, D3, D4 to the former resolution prior to the compaction by the use of the interpolating filters 5, 6, 7.
The output D2 to D4 of respective decimating filters 2 to 4 and the output D5 to D7 of the respective interpolating filters 5 to 7 are inputted into the difference circuit 8, 9, 10 respectively, hereby the difference data D8, D9, D10 is generated. As a result, in the picture coding apparatus 1, the data quantity of the hierarchical data is reduced and the signal power is reduced. The sizes of the difference data D8, D9, D10 and the compacted picture data D4 are 1, 1/4, 1/16, and 1/64 times the size of the input picture data D1 in area, respectively.
The difference data DB to D10 which are obtained from the respective difference circuit 8 to 10 and the compacted picture data D4 which is obtained from the decimating filter 4 are compressed by respective coders 11, 12, 13, 14. As a result, the first, the second, the third, and the fourth hierarchy data D11, D12, D13, and D14 which have different resolutions are sent out, in the stated order, from the respective coders 11, 12, 13, 14 to the transmission line.
The first to the fourth hierarchy data D11 to D14 which are transmitted in this manner are decoded by a picture decoding apparatus shown in FIG. 2. The first to the fourth hierarchy data D11 to D14 are decoded by decoders 21, 22, 23, 24 respectively. As a result, the fourth hierarchy data D24 is outputted from the decoder 24 first.
At the adding circuit 29, the output of the decoder 23 is added to the interpolated data of the fourth hierarchy data D24 which is obtained from the interpolating filter 26, hereby the third hierarchy data D23 is restored. Similarly, at the adding circuit 30, the output of the decoder 22 is added to the interpolated data of the third hierarchy data D23 which is obtained from the interpolating filter 27, hereby the second hierarchy data D22 is restored. Furthermore, at the adding circuit 31, the output of the decoder 21 is added to the interpolated data of the second hierarchy data D22 which is obtained from the interpolating filter 28, hereby the first hierarchy data D21 is restored.
In the picture coding device which realizes such a hierarchical coding method, the input picture data is divided into the plural hierarchy data and coded, therefore the data quantity is inevitably increased by the amount of the hierarchy component. Consequently, there is a problem that the compression efficiency is lowered for the amount of the increasing, in comparison with a high efficiency coding method which does not utilize the hierarchical coding. Besides, there is a problem that in the case where the improvement of the compression efficiency is aimed, the deterioration of picture quality is induced, due to the quantizer which is applied between each hierarchy data.
Considering the above points, the present invention provides a picture coding method and a picture coding apparatus which is able to improve the compression efficiency and is also able to reduce the deterioration of picture quality when hierarchically coding the picture data.
To solve the above problems, in the present invention, a picture coding apparatus for coding inputted picture signal, to recursively generate plural hierarchy data each having a different resolution, comprises: determining and dividing means for determining the way of adaptive division of block which corresponds to the characteristic of the picture data; and transmitting means for transmitting the hierarchically coded data which is obtained from the determining and dividing means. Therefore, the picture data can be divided adaptively into blocks.
Further, in the present invention, a picture coding apparatus for coding inputted picture signal, to sequentially and recursively generate plural hierarchy data each having a different resolution, comprises: determination controlling means for detecting a block activity value of a predetermined block of each hierarchy data excepting the uppermost hierarchy data having the lowest resolution, for generating the division determination flag for determining the way of division of a block on the basis of the block activity value, and when the determined result showing that the block activity value is smaller than the predetermined threshold value is obtained, for generating the division stop flag for stopping the division of the plurality of lower blocks which correspond to the block, and then generating the control signal for stopping the determination of the block activity value of the plurality of lower blocks and the transmission of hierarchy data of the plurality of lower blocks; and transmitting means for transmitting the determination flag of each block along with each coded hierarchy data. Therefore, the decision flag is transmitted along with the picture data which has been divided into blocks.
Further, in the present invention, a picture coding apparatus for coding inputted picture signal, to sequentially and recursively generate plural hierarchy data each having a different resolution, comprises: determination controlling means for detecting the block activity value of a predetermined block of each hierarchy data excepting the uppermost hierarchy data having the lowest resolution, for generating the division determination flag for determining the division of a block based on the block activity value, and when the determined result showing that the block activity value is smaller than the predetermined threshold value is obtained, for temporarily generating the division stop flag for stopping the division of a plurality of lower blocks which correspond to the block, and when the determined result showing that the block activity value of at least one of the plurality of lower blocks is greater than or equal to the predetermined threshold value is obtained, for changing the division stop flag to the division continue flag for continuing the division; and transmitting means for transmitting the determination flag of each block along with each coded hierarchy data. Therefore, the division decision flag for deciding the way of division of block can be confirmed.
Further, in the present invention, a picture coding apparatus for coding inputted picture signal, to sequentially and recursively generate plural hierarchy data each having a different resolution, comprises: determination controlling means for detecting the block activity value of all of the blocks of respective hierarchy data excepting the uppermost hierarchy data having the lowest resolution, for generating the division determination flag for determining the division of the each block based on the block activity value, and when the determined result showing that the block activity value is smaller than the predetermined threshold value is obtained, for generating the division stop flag for stopping the division of the block, and when the determined result showing that the block activity value is greater than or equal to the predetermined threshold value is obtained, for generating the division continue flag for continuing the division of the block; and transmitting means for transmitting the determination flag of each block along with each coded hierarchy data. Therefore, the way of division of block can be decided independently.
Further, in the present invention, a picture coding apparatus for coding inputted picture signal being a plurality of picture forming signals, which have a correlation each other to form a picture, in order to sequentially and recursively generate plural hierarchy data each having a different resolution, comprises determination controlling means for detecting the block activity value which corresponds to the first signal out of a plurality of picture forming signals as to a predetermined block of each hierarchy data excepting the uppermost hierarchy data having the lowest resolution, for generating the division determination flag for determining the division of the block or the division of a lower block which corresponds to the block, and when the determined result showing that the block activity value is smaller than the predetermined threshold value is obtained, for generating the division stop flag for stopping the division of the block or the division of the lower block which corresponds to the block, and when the determined result showing that the block activity value is greater than or equal to the predetermined threshold value is obtained, for generating the division continue flag for continuing the division of the block or the division of the lower block which corresponds to the block, and then for determining the threshold value on the basis of the second signal out of the plurality of picture forming signals. Therefore, the threshold value is set by the first signal such as the luminance signal, and the division of the second signal such as the color signal can be performed.
Further, in the present invention, a picture coding apparatus for coding inputted picture signal which is utilized to sequentially and recursively generate plural hierarchy data each having a different resolution, comprises: threshold value detecting means for detecting a threshold value being a standard of determination of block activity based on the block activity value of all of the blocks of each hierarchy data, to control generated information quantity so as to attain to the target value; determining and dividing means for detecting the block activity of a predetermined block of each hierarchy data excepting the uppermost hierarchy data having the lowest resolution, and for determining the way of division of the block or division of a lower block which corresponds to the block based on the comparison result of the block activity and the threshold value and performing the division; and transmitting means for transmitting the hierarchical coded data which is obtained from the determining and dividing means. Therefore, when the block activity value become less than the predetermined value, (that is when the change of picture become small), the generated information quantity by division processing of the lower hierarchy is controlled.
Furthermore, in the present invention, a picture coding apparatus for coding inputted picture signal, to recursively generate plural hierarchy data each having a different resolution, comprises: determining and dividing means for determining the way of adaptive division of a block which corresponds to the characteristic of the picture data, and for dividing the picture data on the basis of the determined result; and transmitting means for transmitting variable-length data after transmitted the hierarchical coded data obtained from the determining means as fixed-length data. Thereby, transmitting efficiency of data can be improved.